Mechanism for cutting upper thread in a sewing machine



' April 29, 1969 Filed June 16. v 1967 Fig.

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INVENTOR.

Bx; M www TADAsl KozuKA April 29, 1969 MECHANISM FOR CUTTING UPPER THREAD IN A SEWING MACHINE Sheet Filed June 16', 1967 INVENTOR.

API"il 29, 1969 TADAs| Kozu'KA 3,440,985

MECHANISM FOR CUTTING UPPER THREAD IN A SEWING MACHINE Filed June 16, 1967 sheet 5 of 4 INVENTOR. BYLMM MECHANISM FOR CUTTING UPPER THREAD IN A SEWING MACHINE Filed June 16, 196'? TADASI KOZUKA April 29, 1969 Sheet Wm B u 28 v rINVENTOR.

I Hulk-hdd M MW,

United States Patent O U.S. Cl. 112--252 1 Claim ABSTRACT F THE DISCLOSURE Mechanism for cutting the upper thread in a sewing machine comprising a lever means rotatably mounted on said sewing machine, a swinging lever operably coupled with said lever means, a shaft located adjacent to the overhanging arm -of said sewing machine, a cutting device secured to said shaft and operable to cut and grasp the cut end of the thread by the actuation of the shaft, and a presser bar coupled with the stitching means of the sewing machine, said shaft being adapted to be rotated about its axis and, at the same time, to be shifted axially forwardly from the initial retracted position by actuating said lever means through said swing lever thereby advancing said cutting device from the initial position spaced apart from and above the thread cutting position and effecting the cutting of the thread and grasping of the cut thread by the cooperation of presser bar, said shaft being rst retracted axially without rotation thereof by releasing said lever means to retract said cutting device along the line of feed of the cloth with the thread grasped by said cutting device, and shaft thereafter being rotated about its axis thereby causing said cutting device to be moved to its initial position, the thread being released thereby.

Background of the invention The present invention relates to a sewing machine, and more particularly to a mechanism for cutting the upper thread in a sewing machine. The present invention relates particularly to a mechanism in a sewing machine, for cutting off the upper thread when the stitching operation is completed, said cut thread being held in lowered position With the end of the upper thread `being grasped by the mechanism, the upper thread being released after several beginning stitches have been formed.

In the prior art mechanism for cutting the upper thread in a sewing machine the cutter, which is provided in a position rearwardly adjacent to the position where the upper thread is cut, is swung on a shaft and the upper thread is held by a mechanism in a sewing machine after a cutting operation is effected. Since the mechanism is located at a position adjacent to the needle bar, it interferes with the handling of the cloth to be stitches by the operator thereby resulting in inconvenient operation, and further, the upper thread is grasped by the mechanism while several beginning stitches `are being formed after the mechanism has been moved to the initial position in which the cutter is located at a position transverse to the direction of feeding of the cloth to be stitched; hence, the beginning stitches tend to be shifted toward the tensioned upper thread which is grasped by the mechanism, thereby resulting in incorrect positioning of stitches at the beginning of the stitching operation, Further, the mechanism of the prior art for cutting the upper thread is constructed in a such a manner that the cutter of the upper thread is rotated in a direction parallel to the upper surface of the bed of the sewing machine, hence, the length of the upper thread left on the surface of the cloth after cutting thereof is effected is relatively long and the appearance of the inished product is spoiled.

ICC

Summary of the invention The present invention avoids the above disadvantages of the prior art by positioning the driving portions of the mechanism for cutting the upper thread excepting the cutter means for the upper thread as close as possible to the vertical standard and the lower surface of the overhanging arm of the sewing machine, the shaft on which the cutting means for cutting the upper thread are mounted being located parallel to the upper rotary shaft within the overhanging arm, said shaft being adapted not only to be rotated about its axis but also to be shifted axially, thereby permitting the cutting means which, initially, is behind and above the needle bar, to be moved toward the cutting position of the upper thread, so that greater space is provided adjacent to the needle bar on the upper surface of the bed of the sewing machine than heretofore provided by the prior art, the cutter being retracted along the line the cloth A to be stitched is fed and held in position while the cutter is in the lowered position with the leading portion of the upper thread grasped by the cutter, the cutting means being adapted to release the upper thread after several beginning stitches have been formed, and, thereafter, to be returned to the initial position and held in position. Further, since the main driving parts of the present invention are housed in a cover located at the rear side of the overhanging arm, the present invention provides further advantages in that the cloth to be stitched as well as the thread is positively prevented from being contaminated by oil that might leak from the lower portion of the overhanging arm.

Therefore, an object of the invention is to provide a useful and novel mechanism for cutting the upper thread in a sewing machine which avoids the above stated disadvantages inherent in the prior art mechanism.

Another object of the invention is to provide a useful and novel mechanism for cutting the upper thread in a sewing machine in which greater space is provided adjacent to the needle bar on the surface of the bed of the sewing machine than is provided by the prior art mechanism, thereby affording convenient handling of the cloth to be stitched.

A further object of the presen-t invention is to provide a useful and novel mechanism for cutting the upper thread in a sewing machine which make it possible to fonrn correction stitches at the beginning of the stitching operation by providing for the cutter to be retracted along the line the cloth to be stitched is fed while it is kept in a lowered position with the leading end of the upper thread held in position, the cutting means releasing the upper thread after several beginning stitches have been formed and, thereafter, being returned to the initial position and held in position ready for the succeeding operation.

Other objects and advantages of the present invention will be made clear by reading the following description of an embodiment of the present invention in connection with the accompanying drawings illustrating the embodiment of the present invention.

Brief description of the drawings FIG. 1 is an elevational view showing the main parts of an embodiment of the present invention,

FIGS. 2 and 3 are plan views seen in the direction indicated by arrows II-II' in FIG. 1, FIG. 2 showing the mechanism for cutting the upper thread before it is operated, while FIG. 3 shows the same in the retracted position after the cutting operation has been effected,

FIG. 4 is a view seen in the direction indicated by arrows IV-IV in FIG. 1,

FIGS. 5 and 6 are views seen in the direction indicated by arrows V-V in FIG. 4, FIG. 5 showing each part oi the present invention in the state illustrated in FIG. 2

while FIG. 6 shows the same in the state illustrated in FIG. 3,

FIG. 7 is a plan view of thread cutting device of the present invention showing the mounting of the cutting blade with the cover removed to show the mechanism clearly, and

FIG. 8 is an enlarged cross sectional view of the thread cutting device showing the manner in which the upper thread is grasped after the cutting operation is effected.

Description of the preferred embodiment The present invention will be described below referring to the drawings illustrating the preferred embodiment thereof. Referring to FIG. 1, a sewing machine of the conventional type is shown which is provided with a vertical standard 4 integral with an overhanging arm 3 provided with head portion 2 at its forward end, said vertical standard 4 being secured to bed 1 of the sewing machine.

A bearing 6 is rotatably supported by shafts 7, 7 each fixed to bearing supporting members 8, 8 in a direction Itransverse to the axis of the upper rotary shaft (not shown) provided in overhanging arm 3, said bearing supporting members 8, 8 being fixedly mounted on the lower surface of said overhanging arm 3, so that shaft to which is secured the cutting device for effecting the cutting of upper thread and which is rotatably and axially shiftably fitted in said bearing 6, is adapted to be positioned substantially parallel to the axis of said upper rotary -shaft in overhanging arm 3. As shown in FIGS. 1 and 4, a swinging lever 12 is fixedly secured to said shaft 5 at a position adjacent to the right hand end thereof, said lever 12 being provided at its lower end with a cutout 9 so that stop portions 10 and `11 are formed at the lower end of said lever 12 at both sides of said cutout 9. Stepped thread bolt 13 is secured to swinging lever 12 adjacent to the lower end thereof and projects toward said vertical standard 4, a roller being fitted on the shaft portion of said thread bolt 13. L-shaped lever 16 is pivotably secured to said vertical standard 4 by thread bolt -17, the outer end of said lever 16 extending from the rear side of overhanging arm 3 in the direction opposite to the side where the operator is situated, one end of chain 15 being attached to the outer end of lever 16, said chain 15 connecting said lever 16 to the pedal '(not shown) for operation of the cutting mechanism. Stop portion 18 and guide surface 19 are formed at the lower end of said lever 16, said stop portion 18 and guide surface 19 being adapted to engage with said roller 14 on said swinging lever 12. The upper end of lever 16 is provided with inclined surface 21 and fiat surface 20 on the side surface of said lever 16 facing the right hand end of shaft 5, spring 56 being located around shaft 5 between the right hand end of bearing member 6 and lthe left hand end of swinging lever 12 fixedly secured to shaft 5, so that said spring normally urges said sh-aft toward the right thereby forcing the right hand end of said shaft 5 against the left hand side of rthe upper end of said lever 16 where said inclined surface 21 and fiat surface 20 are provided. One end of spring 22 is fixed -to said lever 16 by a bolt mounted on lever 16 adjacent to the outer end thereof and the other end of spring 22 is fixed to the rear side surface of overhanging arm 3 so as `to normally urge said lever 16 clockwise as seen in FIG. 4. Said inclined surface 21 of said lever 16 is located so that inclined surface 21 is adapted to engage with the right hand end of shaft 5 thereby urging shaft 5 toward the left as seen in FIG. 1 when said lever 16 is rotated counterclockwise as seen in FIG. 4 by operating the pedal connected to said lever 16 through chain 15. One end of spring 24 is `fixed to a portion intermediate the length of said swinging lever 12 by bolt 23 mounted on lever 12 Iand the other end of spring 24 is fixed to the side of vertical standard 4, so that spring 24 normally urges said lever 12 clockwise as seen in FIG. 4 thereby urging roller 14 on stepped thread bolt 13 fixed to lever 12 into engagement with stop portion 18 of lever 16.

As seen in FIG. l, stop member 26 provided with recess 25 is threadedly fixed to the side of head portion 2, said recess being adapted to loosely receive and hold the left hand end of shaft 5 for effecting the cutting of the upper thread so that said shaft 5 can be swung about shafts 7, 7' supporting said bearing member 6 and, at the same time, can be shifted axially and rotated about its axis in said bearing member 6, said shaft 5 being normally urged against the lower side of said recess 25 by the action of leaf spring 27 fixed to the lower side of overhanging arm 3. The upper end of supporting member 30 is fixedly secured to said shaft 5 between the left hand end of shaft 5 and the position where said spring 27 contacts shaft 5, said supporting member 30 carrying cutting member 29 threaded thereto, which is provided with lower cutting blade 28, at the lower end of said supporting member 30. Upper cutting member 33 is rotatably secured to said cutting member 29 by stepped bolt 32, said upper cutting member 33 being provided with upper cutting blade 31 which is adapted to cooperate with said lower cutting blade 28 for cutting the upper thread. Said upper cutting member 33 is provided with elongated arcuate hole 34 and a pin 35, the center of the arc of said arcuate hole 34 coinciding with the axis of said stepped bolt 32, said pin 35 projecting upwardly from said upper cutting member 33. Upper thread holder 38 is mounted on the upper surface of said upper cutting member 33 with suitable clearance being provided therebetween by means of washer 36 fitted around bolt 32 and interposed between said upper cutting member 33 and said upper thread holder 38, so that said upper thread holder 38 is adapted to grasp the upper thread by the cooperation with the upper surface of said upper cutting blade 31. Steped bolt 39 is fitted with upper thread holder 38, the shaft portion of said stepped bolt 39 being loosely fitted into said arcuate hole 34 in said upper cutting member 33, the threaded portion of said stepped bolt 39 being threadedly fixed to said cutting member 29.

As shown in FIG. 1, presser foot 41 is fixed to the lower surface of fiat portion 42 which is located above the upper surface of bed 1 adjacent thereto, said fiat portion 42 forming the left hand end of inverted O-shaped presser bar 40, the upper fiat portion of said presser, bar 40 being positioned substantially parallel to said shaft 5, fiat portion 43 formed at the right hand end of said presser bar 40 and located adjacent to the upper surface of bed 1 being rotatably connected to the upper end of connecting rod 44 which passes into bed 1 and is coupled with cam means (not shown) provided on the lower surface of bed 1, so that the cloth to be stitched is shifted in the desired direction by said presser foot 41 by the operation of said connecting rod 44 actuated by said cam means. As shown in FIGS. l, 4 and 5, engaging member 46 is fixed on the rear side of said fiat portion 43 of said presser bar 40 (i.e. the side of fiat portion 43 opposite the side where the operator is situated), said engaging member 46 rotatably carrying engaging plate 45 which overhangs said flat portion 43. A hole 47 is provided in the upper surface of said fiat portion 43 opposite said engaging plate 45, a spring 48 being located in said hole 47 in such a manner that the upper end thereof projects from the upper surface of said fiat portion 43 and is secured to said engaging plate 45 thereby urging the upper surface of said engaging plate 45 against the lower end of said stop portion 10 of swinging lever 12. The O-shaped base portion 51 of resilient stop plate 50 is bolted to the vertical standard 4 as `shown in FIG. 4. Said resilient stop plate 50 is provided with projection 49 (FIG. 5) at the left hand end thereof, said projection 49 being formed by bending the tip portion of said stop plate 50 at a right angle thereto. As shown in FIGS. 4 and 5, said projection 49 is located adjacent to cutout 9 of swinging lever 12. Stop 52 is secured to vertical standard 4 so that said stop 52 limits the horizontal swinging movement of said stop plate 50 toward the vertical standard 4. As shown in FIGS. 2 and 3, engaging plate 55 is fxedly secured to the lower surface of flat portion 42 formed at the left hand end of said presser bar 40, said engaging plate 55 being formed with projections 53 and 54 at the end of engaging plate 55 at both sides thereof, said projections 53 and 54 extending downwardly and being adapted to selectively engage with pin 35 of upper cutting member 33.

As 4shown by solid lines in FIGS. 4, 5 and 7, prior to the actuation of lever 16 which is driven by the pedal, the lower end surface of stop portion of swinging lever 12 is engaged with the upper surface of engaging plate 45 and cutting member 29 is held in its initial position spaced apart obliquely rearwardly from the thread cutting position with upper blade 31 and lower blade 28 held in their opened state by virtue of engagement of pin 35 of upper cutting member 33 with projection 54 of engaging member 55.

Since the present invention is constructed as stated above, when lever 16 is pulled downward by operating the pedal which is connected to lever 16 through chain 15, each of the parts of the mechanism of the present invention is moved to the position las shown in FIGS. 4 and 5 by double dot vchain lines. Thus, lever 16 is rotated counterclockwise against the action of spring 22 as shown in FIG. 4, guide surface 19 of lever 16 causing the rotation of swinging lever 12 together with shaft 5 in a counterclockwise direction against the action of spring 24 by the engagement of roller 14 with said guide surface 19, while inclined surface 21 of lever 16 engages with the rear end of shaft 5 and pushes it against the action of spring 56 as seen in FIG. 2, so that shaft 5 is shifted to the left in bearing member 6. The rotation and axial shifting of shaft 5 effects the resultant movement of cutting member 29 to the nal position together with supporting member 30 secured adjacent to the forward end of shaft 5, in which final position cutting blades 28 and 31 are moved to the positions for grasping the thread 37 leading to the inal stitch of the cloth and needle 57 from their respective initial positions, pin 35 of upper blade 33 engaging with projection 53 of engaging member 55 secured to presser bar 40 which is now at rest, while blades 28 and 31 are moving to their thread cutting position, thereby rotating upper cutting member 33 counterclockwise (FIG. 7) labout the axis of stepped bolt 32, so that the thread. 37 is grasped by upper thread holder 38 and upper blade 31 and thereafter the thread 37 is cut oft by blades 28 and 31. The lower end of stop portion 10, which is engaged with the upper surface of engaging plate 45 prior to the actuation of lever 16, is disengaged from the upper surface of engaging plate 45 by virtue of the movement of swinging lever 12 in the direction indicated by arrow in FIG. 5, when lever 16 is actuated, thereby urging said engaging plate `45 downward against the action of spring 48. Thus the front surface of stop portion 11 of swinging lever 12 moves and urges projection 49 of stop plate 50 and is arrested by projection 49 by the engagement of the left end of stop portion 11 with projection 49 and assumes the position as shown in FIGS. 4 and 5 by double dot chain line.

When the pedal is released, lever 16 is rotated clockwise (FIG. 4) by the action of spring 22, thereby disengaging guide surface 19 of lever 16 from roller 14 of lever 12. However, since projection 49 of stop plate 50 engages with the left end of stop portion 11 of swinging lever 12, the latter is prevented from being rotated clockwise. Upon the rotation of lever 16, the right hand end of shaft 5 is disengaged from the inclined surface 21 of lever 16, and shaft 5 is allowed to be retracted axially in bearing member 6 without rotation thereof to the right as seen in FIG. 3 together with cutting member 29 and supporting member 30 carrying said cutting member 29 with the end portion of thread 37 being grasped between upper thread holder 38 and upper blade 31. As seen in FIG. 5, lever 12 which is retracted together with shaft 5 has the left end of its stop portion 11 engaged with projection 49 of stop plate 50, and, when stop member 52 abuts against stop plate 50, the former prevents the latter from being moved further thereby disengaging stop portion 11 from projection 49 of stop plate 50, so that the left end surface of stop portion 10 of lever 12 abuts against the right hand end of engaging plate 45 as shown in FIGS. 3 and 6.

When the cloth to be stitched is moved between the lower surface of presser foot 41 and the upper surface of needle plate and the sewing machine is operated, presser bar 40 is moved in the direction as indicated by the arrow in FIG. 6 together with connecting rod 44, and, after several beginning stitches have been formed, the left hand end of stop portion 10 of swinging lever 12 is disengaged from the right hand end of engaging plate 45 thereby permitting the rotation of swinging lever 12 in the clockwise direction (FIG. 4) by the action of spring 24, so that the lower end of stop portion 10 is positioned above the upper surface of engaging plate 45. And, at the same time, shaft 5 is rotated clockwise together with supporting member 30 and cutting member 29, whereby pin 35 of upper cutting member 33- abuts against projection 54 of engaging plate 55 which is being moved, thereby rotating upper cutting member 33 clockwise (FIG. 7) so that thread 37 which has been grasped between upper thread holder 38 and upper blade 31 is released and cutting member 29 is moved to its initial position as shown in FIG. l.

Since the present invention thus far described provides the shaft 5, swinging lever 12 and other driving parts excepting cutting member 29 in positions adjacent to the lower side of overhanging arrn 3 and vertical standard 4, permitting shaft 5 to which is secured a cutting device for effecting the cutting of upper thread and which is arranged substantially parallel to the upper rotary shaft in overhanging arm 3 to be rotated about its axis as well las to be shifted axially, and permitting cutting blades 28 and 31 which are normally held in their initial position to be moved to their cutting position during the operation, it is possible by the present invention to cut the upper thread in a shorter length of time than the prior art, and, since greater space is provided adjacent to the needle bar on the upper surface of bed 1 by the present invention than in the prior art, it is easier to handle the cloth to be stitched, and further, since cutting blades 28 and 31 which grasp the end of the upper thread after it has been cut olf are held in a retracted position along the line the cloth is fed from the thread cutting position until several beginning stitches have been formed, proper stitches can be obtained by the present invention without the line of stitches being drawn toward the tensioned upper thread pulled from the direction transverse to the line of feeding of the cloth as is the case in the prior art wherein the cutting device grasping the thread is held in position transverse to the line of feed of the cloth after the cutting operation is effected.

It must be understood that the embodiment described above is merely an illustration of the present invention and that the present invention is not limited in detail to the embodiment shown but the scope of the present invention is defined by the appended claim.

What is claimed is:

1. A mechanism for cutting the upper thread in a sewing machine having an overhanging arm with the needle at the end thereof and a presser bar extending along said arm, said mechanism comprising a shaft positioned adjacent the overhanging arm of said sewing machine anc mounted for axial sliding and rotational movement, z swinging lever mounted on said shaft, a lever mean: rotatably mounted on the side of said sewing machine ancl engageable with said shaft for axially sliding said shaf from an initial to a shifted position and engaging sai( swinging lever for rotating said shaft from an initia to a rotated position when said lever means is rotated a cutting device mounted on said shaft and engaged with said presser bar for being operated to cut and grasp the cut end of the thread when the said shaft is rotated and shifted axially, swinging lever holding means for engaging and holding the swinging lever in its rotated position when it is in the axially shifted position, swinging lever retaining means on said presser bar and engageable with said swinging lever for temporarily retaining said swinging lever in the rotated position when it is returned to its initial position, and biasing means engage with said shaft biasing it axially and rotationally to its initial position, rotation of the lever means rotates said swinging lever and thus said shaft and, at the same time, shifts said shaft axially to the shifted position and advances said cutting device from an initial position spaced from and offset laterally from the thread cutting position with said cutting device being held in the open state to a cutting and grasping thread holding position, and when said lever means is returned to its initial position, said shaft is retracted axially by said biasing means to retract said cutting device from said thread cutting position along a line of the cloth to be stitched with the thread still being held by said cutting device, said holding means initially holding said swinging lever from returning to its initial position and thus preventing rotation of said shaft to its initial position, and said swinging lever thereafter being held by said presser bar retaining means, said presser bar being shifted after several beginning stitches have been formed for releasing said swinging lever from said retaining means so that said shaft is rotated about its axis to its initial position, thereby moving said cutting device to its initial position and releasing the thread.

References Cited UNITED STATES PATENTS 735,432 8/1903 Allen 112-252 737,122 8/1903 Lyons l12-252 1,021,156 3/1912 Lyons 112-252 1,358,847 11/1920 Hill 112-252 HERBERT F. ROSS, Primary Examiner. 

